1. Field of the Invention
This invention relates to an amorphous semiconductor device having a structure which is operable as a color sensor.
2. Description of the Prior Art
FIG. 11 shows a conventional semiconductor color sensor comprising a p-Si crystal layer 1, an n-Si crystal layer 2 and a p-Si crystal layer 3, on each of which electrodes I, II and III are disposed, respectively, to form, in Si crystal chips, double photodetectors, one of which is composed of a photodiode containing a PN junction at the upper position therein, having a sensitivity to short wavelengths and the other of which is a photodiode containing another PN junction at the lower position therein, having a sensitivity to long wavelengths. The upper photodiode has the function of a filter for the lower photodiode. The ratio of the short-circuit current between the electrodes I and II of the upper photodiode to the short-circuit current between the electrodes II and III of the lower photodiode is represented by a first-order function of the wavelength of the incident light ray thereupon, and thus this conventional semiconductor color sensor can detect the color of an incident light ray.